Taurine can be referred to as 2-aminoethylsulfonic acid and is of the formula H2NCH2CH2SO3H. Taurine is an extremely useful compound because it per se has such pharmacological effects as detoxification effect, fatigue-relieving effect and nourishing and tonifying effect. As a result, taurine finds wide applications as an essential ingredient for human and animal nutrition.
Many chemical synthetic methods have been known in the prior arts for the preparation of taurine and related derivatives. The following two methods have been used in industry to manufacture over 60,000 tons of taurine per year, starting from ethylene oxide (the EO process) or monoethanolamine (the MEA process).
According to the EO process disclosed in U.S. Pat. Nos. U.S. Pat. No. 8,609,890, U.S. Pat. No. 9,061,976, U.S. Pat. No. 9,428,450 and U.S. Pat. No. 9,428,451, ethylene oxide is reacted with sodium bisulfite to obtain sodium isethionate, which undergoes ammonolysis reaction to yield sodium taurinate. Neutralization with an acid results in a mixture of taurine and inorganic salt. During the reaction of ethylene oxide with aqueous sodium bisulfite, significant amount of ethylene glycol and diethylene glycol is formed as byproducts. After ammonolysis reaction of the crude sodium isethionate, ethanolamine is also formed in the process. After the separation of taurine and inorganic salt, typically sodium sulfate, current industrial process leaves behind a large amount of waste stream containing glycols, monoethanolamine, sodium taurinates, and sodium isethionate.
Copending U.S. Ser. No. 15/268,071 discloses a novel variation of the EO process for producing taurine from ammonium isethionate, which is prepared from the reaction of ethylene oxide with aqueous ammonium bisulfite. According to U.S. Pat. Nos. 5,646,320, U.S. Pat. No. 5,739,365, and U.S. Pat. No. 5,763,632, the reaction of ethylene oxide with ammonium bisulfite produces some ethylene glycol and monoethanolamine as byproducts even under best controlled reaction conditions. After concentration and crystallization of ammonium isethionate, the mother liquor is enriched with monoethanolamine as isethionate salt and ethylene glycol, which make further isolation of ammonium isethionate difficult. When the crude ammonium isethionate is used in the cyclic process for producing taurine, accumulation of monoethanolamine and ethylene glycol in the process renders a large purge of mother liquor necessary.
According to the MEA process disclosed in U.S. Pat. No. 9,145,359, monoethanolamine is reacted first with sulfuric acid to afford 2-aminoethyl hydrogen sulfonate ester, which undergoes sulfonation reaction with ammonium sulfite to yield a mixture of taurine and ammonium sulfate. During the sulfonation reaction, up to 15% of the intermediate ester is hydrolyzed to monoethanolamine, which is left in the waste stream as its sulfate salt, along with ammonium sulfite and ammonium sulfate, or along with sodium sulfite and sodium sulfate when sodium sulfite is used as sulfonation agent.
It is the principal object of the present invention to disclose an extraction process for recovering aminoalcohols and glycols from aqueous streams of taurine production from ethylene oxide or monoethanolamine. According to the process disclosed in the present invention, the aqueous streams, after removing of aminoalcohols and glycols, can be returned to the cyclic process for the production of taurine.